Butene recovery

ABSTRACT

Butenes are recovered from hydrocarbon cracking streams by a process which comprises (1) distillation of the crude feed stream to remove C5 and heavier materials, (2) desulfurization of the butene-containing stream, (3) partial hydrogenation of the desulfurized butene-containing stream to convert diolefins to monoolefins and (4) distillation of the hydrogenated butenecontaining stream to remove C3 and lighter materials. The recovered butene can be oxidized to form methyl ethyl ketone or hydrogenated to form valeraldehydes.

United States Patent Hagemeyer, Jr. et al.

[ 51 June 20, 1972 [54) BUTENE RECOVERY [72] Inventors: Hugh J. lhgemeyer, Jr., Longview; Harry F. Gem, White Oak, both of Tex.

[73] Assignee: Eastman Kodak Company, Rochester,

[22] Filed: June 10, 1970 [2|] Appl. No.: 44,961

[$2] [1.8. CI. ..260/677 A, 208/255 [5|] lnt. ..C07cll/02 [58] Field of Search ..260/677, 677 A, 677 H; 208/92, 208/99, 255

[5 6] References Cited UNITED STATES PATENTS 2.671.754 3/l954 De Rosset et al. ........208/99 X 3,004,083 I0! I96] Siedenstrang et al ..260/677 A 3,239,454 3/]966 Streed et a]. JOB/255 X 2,042.298 5/ l 936 Davis ..208/255 3,470,085 9/1969 Parker ..260/677 H Primary Examiner-Delbert E. Gantz Assistant Examiner-J. Nelson Attorney-Cecil B. Quillen. Jr. and Daniel B. Reece. Ill

[57] ABSTRACT Butenes are recovered from hydrocarbon cracking streams by a process which comprises (I) distillation of the crude feed stream to remove C, and heavier materials, (2) desulfurization of the butene-containing stream, (3) partial hydrogenation of the desulfurized butane-containing stream to convert diolefins to monoolefins and (4) distillation of the hydrogenated butene-containing stream to remove C and lighter materials. The recovered butene can be oxidized to form methyl ethyl ketone or hydrogenated to four: valeraldehydes.

4 Claims, I Drawing Figure PATENTEDJMQ r912 3,671 ,603

HUGH J HAGEMEYER,JR. HARRY F 6055 {NV TO BW QQ JUNE ATTORNEYS BU'IENE RECOVERY This invention relates to a novel chemical process and more particularly to a novel process for recovery of butene from hydrocarbon cracking streams. More specifically, it pertains to the removal of undesirable components form the butene containing stream by distillation, adsorption and hydrogenation in a particular sequence, and of the use of the purified butene stream. This invention also relates to the oxidation of the recovered butene to form methyl ethyl ketone and/or the oxonation of the butene to form valeraldehydes.

In the cracking of hydrocarbons, butenerich side streams are produced. Such streams are often produced in appreciable quantities and it would be thus economically advantageous to utilize these materials rather than to exhaust them as waste, for example, by flaring. However, these side streams are contaminated with a large number of undesirable components. As an example, in the cracking of propane to form propylene and ethylene, a butene-rich stream is discharged from the base of the depropanizer column. This stream contains C, through C. hydrocarbons, C, through C, olefins, C. and C, diolefins, benzene and other aromatics, acetylenes and some sulfur compounds. This crude stream may be burned or recycled to the cracking furnace. However, it is not a particularly economical fuel because of its low heat content and its value as cracking plant feed is also relatively low because of the poor yields to ethylene and the large amount of coking which takes place.

The conversion of butene-l and butene-2 to useful chemicals such as methyl ethyl ketone and valeraldehydes is known. Therefore, the butene value of the butene-containing byproduct stream from hydrocarbon cracking processes would be considerably enhanced if used as a feed to hydrolytic olefin oxidation unit to form methyl ethyl ketone or to an oxonation unit to form valeraldehydes. In each instance, however, the feed must be essentially free of sulfur compounds since they are catalyst poisons when present in concentrations greater than 3 ppm. In addition, all diolefins and acetylenes must be removed because they form very stable complexes with the palladium chloride catalyst of the oxidation unit or the cobalt catalyst of the oxonation reaction. These stable complexes are not active as catalysts; therefore, the desired oxonation of oxidation reaction is severely retarded or completely stopped if the catalyst is converted to such complexes. The presence of C, and heavier hydrocarbons is deleterious since they form azeotropes with the ketone product of the oxidation reaction thus impairing yield and product quality; these materials are difiicult to remove in the purification of valeraldehydes. Since the propane which is present in the butene-rich stream is inert, its presence in a reactor system will lower the production capacity of the system and hence it is desirable if the propane can also be removed from the butene-rich stream economically.

It has been known to purify multicomponent streams by distillation. However, the purification by distillation of the multicomponent butenerich side stream from a hydrocarbon cracking side stream to obtain a product consisting essentially of butene-l and butene-2 is not only extremely difficult but is also economically unattractive. Butadiene, which constitutes one of the major components of the stream, boils within 1 of butene- 1. Hence the separation of these two materials cannot be readily effected by simple distillation procedures. To purify such mixtures, extractive distillation methods combining fractionation and solvent extraction or a series of vacuum distillations must be employed. In either case, such purification techniques are costly. To further complicate the purification of butene-containing stream, the boiling point of butadiene is between that of butene-1 and butene-2. It is therefore necessary to purify butent-l and butene-2 separately in addition to separating them from butadiene thereby making purification by distillation even more economically unattractive. Further, the removal of the sulfur-containing materials from the hutene-containing stream to a concentration of 3 ppm. or less cannot readily be effected by distillation.

An object of this invention is to provide a novel process for the recovery of butene from butene-rich hydrocarbon cracking side streams.

Another object is to provide a process for the removal of undesirable components from the butene-rich stream in a particular sequence and of its subsequent use.

Still another object is to provide a process for the oxidation of the recovered butene to form methyl ethyl ketone and/or the oxonation of the butene to form valeraldehydes.

And still another object is to provide a method of recovery and purification which produces butenes suitable as feed stock for catalytic chemical reactions.

These and other objects are attained by the practice of this invention which, briefly, comprises four steps which are: (I) distillation of the crude stream, (2) removal of remaining sulfur compounds, (3) partial hydrogenation and (4) distillation of the purified stream to recover the butene. The relatively pure butene may be fed directly to an olefin oxidation unit to form methyl ethyl ketone or it also may be mixed with ethylene and fed to the oxidation unit to form a mixed product of acetaldehyde and methyl ethyl ketone.

The process for preparing purified butene from a crude olefin stream comprises the four steps in the particular sequence more specifically described below.

The first step comprises the distillation of the crude stream to remove all Q and heavier materials. This distillation is run at a temperature of 30 to 250C. and a pressure of mo to 250 pounds per square inch gage (hereinafler referred to as psig), and preferably at $0 to 200 C. and 150 to 225 psig. It is run so that the overhead product will contain less than 0. l percent material boiling above trans-butene-Z. A difference in boiling points of 32 C. exists between trans-butene-Z and isopentane, which is the lowest boiling of the heavier hydrocarbon materials. This separation must be effected first in order to remove not only the higher-boiling hydrocarbon, but also a substantial proportion of the sulfur compounds The high-boiling hydrocarbon compounds must be removed because they are not only deleterious to the catalyst of the aforementioned butene oxidation and oxonation reaction but they are also detrimental to the sulfur-removal catalyst and hydrogenation catalysts employed in the subsequent steps essential to the process of the invention.

The second step comprises the removal of any remaining sulfur compounds in the butene-containing product from the distillation step. in the distillation the sulfur concentration is reduced, for example, from 30 to ID ppm. This remaining sulfur is removed at this point so that it will not poison the hydrogenation catalyst. The preferred method of sulfur removal is by adsorption on activated carbon pellets. Commercial catalysts suitable for this operation are Girdler's 0-3215 or Catalyst and Chemicals lncorporated's C-8-l This process is run at pressures from one atmosphere to several atmospheres and at temperatures form 0 to 50 C. This process may be run in the liquid phase or in the vapor phase. The preferred conditions are 100 to 250 psig and It? to 30 C. The product from this bed contains less than 1 ppm. sulfur and typical analysis is 0.3 ppm. sulfur.

The third step comprises the partial hydrogenation of the butadiene to form butene. By the hydrogenation of butadiene, which makes up a large portion of the C. fraction, to butene it is possible to recover a large portion of the butadiene originally present in the stream. The partial hydrogenation may be run at pressures from one atmosphere to several atmospheres and temperatures from 50 to 200 C., preferably at 100 to 300 psig and between 60 and I30 C., respectively. A slight molar excess of hydrogen to butadiene in the feed is used, for example, a l.l:1 molar ratio. The hydrogenation catalyst may be a supported palladium catalyst. Commercial catalysts available for this selective reduction are Girdler's G-and 6-68 or Harshaw's Pd-OSOIT. Control of the hydrogenation within the limits specified is essential to prevent hydrogenation of butadiene and butene to butane. Under these conditions yields and conversions to butene in excess of percent butenes is less than 0. l percent.

The fourth step is the distillation of this purified stream to remove propane and propylene. This separation is done last because the excess propane is used as a diluent in the hydrogenation step to absorb some of the heat of reaction. This distillation is operated at a temperature of about 20 to 200 C. and at a pressure of about 150 to 325 psig and preferably at 40 to 150 C. and 200 to 300 psig, respectively. The best pressure is 250 psig. The overhead product is essentially all propane and propylene. The base product is the final butene cut and contains only small amounts of butane, isobutane, and propane as impurities.

The process of the invention may be further illustrated by referring to the drawing. in the process, the crude stream is introduced into the distillation column 1 via a conduit 2. The high boiling or heavier materials are removed from the bottom of the distillation column via a conduit 3. The low boiling compounds are removed from the top of the distillation column 1 via a conduit 4 and cooled by the cooler 5. A portion of the low boiling material is returned to the top of the distillation column 1 via a conduit 6. The remaining material is pumped into the top of the sulfur removal bed 9 by the pump 7 via a conduit 8. The desulfurized product is removed from the bottom of the sulfur removal bed 9 via a conduit 10, cooled by the cooler 11 and introduced into the top of the hydrogenation reactor 14. Hydrogen is introduced into the line 10 via a conduit 12. The hydrogenated product is removed from the hydrogenation reactor 14 via a conduit 15 and is cooled by a cooler 16. A portion of the product from the cooler 16 is recycled to the hydrogenation reactor 14 by a pump 19 via a conduit 13 and the remaining portion of the product is pumped into the distillation column 20 by the pump 18 via a conduit 17. The purified butene product is removed from the distillation column 20 via a conduit 21. The compounds having a boiling point below that of butene are removed from the distillation column 20 via a conduit 22 and cooled by the cooler 23. A portion is recycled to the top of the distillation column 20 via a conduit 24 and the remaining portion is removed from the distillation column via a conduit 25.

The following examples illustrate the novel process of this invention.

EXAMPLE 1 This example employs the process and apparatus illustrated in the drawing and described hereinabove. A butene-containing stream, of the analysis shown in Table 1 under point A, refined to give a relatively pure butene feed. The material was first distilled to remove all materials boiling higher than butene-2. The distillation was run at 180 psig and at a temperature, in the top of the column, of about C. and in the bottom of the column of about 145 C. The high boiling residue has an analysis as designated at point B. The overhead product, having an analysis as given under point C, from the distillation column was fed to a sulfur removal bed packed with Girdler G-32E activated carbon pellets. The sulfurremoval bed was operated at a temperature of about 20 C. and a pressure of about 210 psig. The sulfur concentration was reduced to 0.3 ppm. The discharge from this bed having an analysis at point D was fed to a hydrogenation reactor packed with Girdler 0-55 palladium or alumina catalyst. The heat of reaction may be absorbed by recycling a portion of the product to the hydrogenation reactor. The hydrogenation reactor was run at about C., and at about 200 psig. A 1.1:1 molar ratio of hydrogen to butadiene was fed to the reactor. The hydrogen flow rate was 4.3 pounds per hour. The product from the hydrogenation had an analysis designated at point E. A second and final distillation was then run to remove excess propane and propylene. This distillation was run at about 250 psig. The temperature in the top of the column was about 51 C. The analysis of the stream at point 0 is that of the final butene product. An analysis of the lower boiling stream is given at point F.

EXAMPLE 2 A mixed butene stream (0.163 lb.-mole) recovered according to the process shown in Example 1 having the following analysis:

43 percent butene-1 40 percent butene-2 9 percent isobutylene 8 propane and butane is fed into percent propane reactor along with 0.13 lb.-mole carbon monoxide and hydrogen. The butene is reacted with the carbon monoxide and hydrogen at 175 C. and 2,500 psig using a supported cobalt catalyst. The material is removed from the reactor, cooled and introduced into a high pressure liquid/vapor separator. A portion of the material is recycled back to the reactor for further treatment. The remaining material is removed from the separator, passed through an expansion valve and introduced into the low pressure liquid/vapor separator. C H (0.023 lb.-mole) and 3 H, and C H (0.0354 1b.-mole) are removed from the top of the separator and n-pentanal (0.056 lb.-mole), Z-methylbutanal (0.038 lb.-mole) and 3-methybutanal (0.011 lb.-mole) are removed from the bottom of the separator. A conversion of 70 percent and a yield of 83 percent to pentanals lreobtalned The ration of n-pentanal to 2-methylbutanal to 3-methylbutanal is 6:4: 1. The space time yield is 14.8 pounds per liter hour.

ill

EXAMPLE 3 A mixed butene stream (5.08 g.-mole) recovered from the depropanizer column base overflow of a propane thermal cracking unit, such as used in Example 1, having the following analysis:

43 percent butene-1 40 percent butene-2 9 percent isobutylene 8 percent propane and butane is fed to a two-stage oxidation unit. The butene stream is fed into the base of a reactor (oxidizer). Prior to the introduction of the said butene stream, the reactor is charged with an aqueous catalytic solution containing copper chloride, palladium chloride and hydrochloric acid. The butene stream is oxidized in the reactor and passed to a flash column. The product is removed from the top of the flash column and cooled. Methyl ethyl ketone is removed from the cooler and collected. The remaining compounds including unreacted butene are removed from the cooler. A conversion of 42 percent and a yield of 94 percent methyl ethyl ketone were obtained with a space-time yield of grams per liter-hour. Butene accountability was 98 percent.

TABLE 1 Point in FIG. 1

Analysis A B C I) E G Propane, percent 32.0 37. 2 37.2 36.4 3. 4 Propyl ne, percent 2.0 3 2. 3 2. 2 0. 0 lsobutano, percent. 0. 5 ti 0. ti 0. 6 0.7 n-Butanu, percent.. 2.0 .3 2.3 2.4 3,8 lluteno-l, percent 22. 0 B 25. 6 2B. 3 44. 0 isobutylene, percent l5. 0 8 5. 8 5. 5 B. 6 trans-But|-ne-2. percnnL. 8. 0 3 9. 3 10. 4 25.4 cis-liutene-Q, percent. 4. ll 6 4. 6 8. ll 14. 2 Butadivnv. ercent.... 10.5 .2 12.2 0.06 0.1 C-,. ('z. C. 7;,per0ent 14.0 .0 0.0 0.0 Sulfur. p.p.m 30. 0 0 0.3 0. 3 0. 0 0. 5 Flow rate, Eli hr V 100.0 .0 86.0 00.3 32.1 58.2

The invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

I. A process for the recovery of butenes from the residue of a hydrocarbon cracking operation to produce olefins which comprises separating by distillation the C, and lighter hydrocarbons from all heavier and higher boiling materials, desulfurizing the lighter hydrocarbon portion by contacting with activated carbon, partially hydrogenating the butadiene present in the lighter hydrocarbon portion and separating by distillation the C, and lighter hydrocarbons to give a relatively pure butene stream.

2. The process according to claim 1 wherein the first separation by distillation is done at a temperature of about 30 to 250 C. and at a pressure of about l5 to 450 psig, the desulfurization is done at a temperature of about to 50 C. and a pressure of about I00 to 250 psig by contacting the feed with activated carbon, the hydrogenation is carried out at a temperature of about 50 to 200 C. and at a pressure of IS to 450 psig and the second distillation is done at a temperature of about 20 to 200 C. and at a pressure of about 150 to 32$ P 8- 3. The process according to claim 1 wherein the first separation by distillation is done at a temperature of about 50 to 200 C. and at a pressure of about 150 to 225 psig, the dew]- furization is done at a temperature of about 10 to 30 C. and at a pressure of about I00 to 250 psig in the presence of activated carbon, the hydrogenation is carried out at a temperature of about 60 to C. and at a pressure of about I00 to 300 psig and the second distillation is carried out at a temperature of about 40 to I50 C. and at a pressure of about 200 to 300 psig.

4. The process according to claim 2 wherein the desulfurization is carried out in the presence of activated carbon pellets and the hydrogenation is done in the presence of a supported palladium metal catalyst.

i i i i I 

2. The process according to claim 1 wherein the first separation by distillation is done at a temperature of about 30* to 250* C. and at a pressure of about 15 to 450 psig, the desulfurization is done at a temperature of about * to 50* C. and a pressure of about 100 to 250 psig by contacting the feed with activated carbon, the hydrogenation is carried out at a temperature of about 50* to 200* C. and at a pressure of 15 to 450 psig and the second distillation is done at a temperature of about 20* to 200* C. and at a pressure of about 150 to 325 psig.
 3. The process according to claim 1 wherein the first separation by distillation is done at a temperature of about 50* to 200* C. and at a pressure of about 150 to 225 psig, the desulfurization is done at a temperature of about 10* to 30* C. and at a pressure of about 100 to 250 psig in the presence of activated carbon, the hydrogenation is carried out at a temperature of about 60* to 130* C. and at a pressure of about 100 to 300 psig and the second distillation is carried out at a temperature of about 40* to 150* C. and at a pressure of about 200 to 300 psig.
 4. The process according to claim 2 wherein the desulfurization is carried out in the presence of activated carbon pellets and the hydrogenation is done in the presence of a supported palladium metal catalyst. 